Tuesday, July 9, 2013

Provincetown's Beach Grass Can be Artistic as Well as Functional


"Compass grass" traces circles around its stem in continuous gusts of wind.

Beginning back in the 1960s the National Park Service started a program that would help to control the erosion of beaches and dunes in the Provincetown area by planting rows of beach grasses in spots exposed to strong winds or to waves along the shoreline. These grasses were planted to help to stabilize the dunes against the force of the wind, and to keep the beaches from eroding under the constant pressure of waves and tides rolling in along the shore. These grasses also help to defend the beaches from serious storms that can carry away acres of sand from the shoreline overnight.
The grasses on the dunes and sandy hillsides surrounding Provincetown are ammophila breviligulata, or cape American beach grass. This grass can grow quite well even in arid locations, clinging tenaciously to sandy hillsides in even the worst of conditions served up by Mother Nature. It's been planted all along the fore dune (the "front" dune, on the edge of the beach) at Race Point and Herring Cove beaches as well, to help the shoreline resist the wind and the waves that would carry away tons of sand from these areas every year if it weren't for the erosion control provided by these hardy grasses.
The beach grass proliferates on its own by sending out a tremendous root system well below the surface, starting new shoots from rhizomes growing among these roots. A rhizome is a kind of chunky root that sends "fingers" growing in different directions, the way ginger grows. The nodes of the rhizome can each start a new clump of grass growing by sending out a runner under the sand, and blades of grass can spring up several feet from the original culm (stem) and will sometimes show up as a straight line of new grasses fighting their way up to the surface from a root stretching out far below the sandy, windswept hillsides.
After some time these single blades of very tall grass produce a few more stems, forming a little clump of grass as seen in the photo above. These grasses bend in a strong wind, and the tips of the grass often brush against the sand. When the wind blows in steady gusts, the tips of the grasses move with these gusts, often tracing a circle in the sand around these sturdy stems.
Nature makes its own art with the circles drawn by the compass grass and the
long, slender shadows cast by single stems of grass at just the right time of day.
We'll sometimes see hillsides covered with graceful circles surrounding small bunches of beach grass, creating a lovely bit of natural art in the sand. These circles remind us of lines traced by a compass, with one point fixed in the center while the other point rotates around it. With each gust of wind, a tall blade of grass will trace a bit of a circle. As the wind shifts, another part of the circle will be etched. Winds gusting steadily through the day can eventually carve deep circles in the sand. And that is how these individual clusters of "compass grass" got their nickname.

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